Critical Wear Parts: O-Ring and Faucet Seat
The most frequent service call on the K-6665 is a dripping dispenser faucet. The faucet uses a spring-loaded lever mechanism with a rubber seat and O-ring seal. Over time, mineral deposits from hard water etch the seat and cause weeping at the nozzle. Kohler replacement O-ring kit GP77759 fits the K-6665 faucet body and restores a watertight seal. Replacement takes 20 minutes: remove the faucet lever screw, lift out the spring and seat assembly, swap the O-ring, and reassemble.
Heating Element Replacement
The K-6665 uses an immersion heating element rated 1500W at 120V. If the unit stops heating and the GFCI outlet tests live, the element may have failed. Kohler part K-1001082 is the complete tank and element assembly -- Kohler does not sell the element alone, so the service procedure is tank replacement rather than element-only swap. A replacement tank takes approximately 45 minutes to install following the same steps as original installation.
Supply Line and Compression Fitting Maintenance
The 3/8-inch compression supply line should be inspected annually for kinking, corrosion at the ferrule, or mineral crust at the tank inlet. Replace the supply line every 5 years as preventive maintenance regardless of visible condition -- compression fittings on plastic lines can develop micro-cracks that are not visible externally. Use a braided stainless supply line rather than a plastic-jacketed line for longer service life in the hot, humid environment under a kitchen sink.
Tank Descaling Procedure
In hard water areas (above 7 grains per gallon), mineral scale accumulates inside the tank and reduces heating efficiency. Descale annually by shutting off the supply, draining the tank completely through the faucet, then filling the tank with a solution of 2 tablespoons white vinegar per quart of water. Allow to soak for 4 hours, then drain and flush with fresh water twice before returning to service. Do not use commercial descalers not approved by Kohler -- citric acid products can damage the stainless tank interior coating.
Faucet Finish Restoration
Kohler Vibrant Stainless (VS) and Brushed Vibrant (BV) finishes on the dispenser faucet are PVD-coated and resist tarnishing, but steam and hard water spots will accumulate around the nozzle. Clean with a damp cloth and Kohler-approved cleaner (avoid bleach and abrasive pads). If the PVD finish is scratched through to the base metal, the faucet body (part K-6665-faucet-body) can be ordered as a standalone replacement without buying the full tank assembly.